If you use mount -o remount,, these extra options always get appended to the existing ones in /etc/mtab. This has the effect that on suspend/resume, mounted USB drives keep growing options like

/dev/sdc1 on /media/LaCie type ext4 (rw,nosuid,nodev,commit=600,commit=600,commit=0,commit=600,commit=0,commit=600,commit=0,commit=0,commit=0,commit=600,commit=0,commit=0,commit=600,commit=0,commit=600,commit=600,commit=0,uhelper=udisks)

because of a pm-utils hook (/usr/lib/pm-utils/power.d/journal-commit).

Reproducer:

$ sudo modprobe scsi_debug

ATTENTION! MAKE TRIPLE-SURE ABOUT THE DEVICE NAME HERE! it's the fake one from scsi_debug

$ sudo mkfs.ext4 /dev/sdb
$ sudo mount /dev/sdb /mnt
$ grep sdb /etc/mtab
/dev/sdb /mnt ext4 rw 0 0

$ sudo mount -o remount,commit=600 /dev/sdb
$ grep sdb /etc/mtab
/dev/sdb /mnt ext4 rw,commit=600 0 0

$ sudo mount -o remount,commit=600 /dev/sdb
$ grep sdb /etc/mtab
/dev/sdb /mnt ext4 rw,commit=600,commit=600 0 0